With the integration of power technology and information technology, the device utilizing automation technology, computer technology and communication technology can be used as the physical avatar of people, and can extend the people's visual sense and haptic sense, so it can realize the user's exploration of the distant environment.
First of all, the attempts to extend the people's visual sense and haptic sense with avatars were implemented in currently very popular WLAN (Wireless Local Area Network). The WLAN has the high bandwidth, and can transmit video data and haptic data smoothly. A video acquisition device with a camera can provide video data, and a joystick that is subordinate to PC can provide haptic data, which can be used to control the movement speed of the mobile video acquisition device. Some universities and research institutes have studied the transmission of video data and haptic data through WLAN. In LAN, the client/server architecture is used to transmit video data and haptic data with TCP protocol or UDP protocol. Shandong Electric Power Research Institute of China developed a substation inspect robot, and a video acquisition device is located in the mobile body of the robot, which is connected through WLAN with the computer for human-machine interaction through WLAN. The computer receives various instructions of the operator and gives the instructions to the mobile body of robot. In the other hand, the computer analyzes the images from the robot. If the images aren't normal, the computer transmits data to a higher level and gives alarms. The communication distance of WLAN is short, and it limits the application scope of the technology which is used to transmit video data and haptic data through LAN.
With the development of the 3G telecommunication network, the long-distance transmission of video data and haptic data becomes possible, and telecom operators in many countries have started to attempt it. Patent Application Publication CN200910176998 provides a method for transmitting video data and haptic data and provides a video acquisition device. A user views the video acquired by video acquisition device in the phone screen. And with the phone keyboard, user can input haptic data, such as going forward, going backward, turning left, turning right and the like, which are transmitted to the video acquisition device and are used to control its motion. In this system, the cost of data transmission through 3G network is relative higher. And in order to connect data channels between the phone and the data acquisition device, the complex telecom signaling is required. In addition, the haptic signals inputted from phone keyboard are simple, so the control effect on the video acquisition device is not good enough.
In the dedicated communication channel, video data and haptic data can be transmitted to more distant place. The lunar rover vehicle is an example. The operator sits in front of the screen of the ground control center, and the lunar rover returns images of the moon surface which are displayed on the screen. According to these images, the operator gives the control instructions. The haptic data including the control instructions are transmitted to the lunar rover vehicle, and help the lunar rover to avoid obstacle and go ahead. Due to the dedicated communication channel, the cost is very high. In addition, there is single-to-single communication between the ground computer and the lunar rover vehicle, and the large-scale communication network is not formed.
On the Internet, P2P (Peer to Peer) technology is applied more and more widely. With the P2P Technology, multimedia files can be transferred directly between two computers which have no globally accessible IP address (also known as public IP address). The computers are connected to the Internet through routes with globally accessible IP address. The IP address of the computer is also called private IP address. Both of the two computers can communicate with the server in the Internet. The routers perform the Network Address Translation (NAT). The source IP address and port number PortA of the UDP packet from the computer are replaced with the router's IP address and port number PortB, which is allocated to the computer by the router. And the router transmits the packets whose destination port number is PortB to the computer. The two computers can transmit the file data directly, after the public IP address and communication port number PortB of the opposite party is known through the server. P2P is well-known technology, and it isn't described in detail here. The distance between the two computers may be long, and these computers may be located in different buildings of one city, and may be located in different cities, and may be located in different countries. In addition, most of the computers having access to the Internet can transfer the multimedia files to each other with the P2P technology, and a network of multiple computers versus multiple computers is formed.
Compared with wireless local area network, the existing Internet has the advantage of long-distance.
Compared with 3G telecommunication network, the existing Internet has the advantage of low-cost.
Compared with dedicated communication channels, the advantage of the existing Internet is that there are many positions having access to Internet.